Improved Performance on Moving-Mass Hopping Robots with Parallel Elasticity

Abstract

Robotic Hopping is challenging from the perspective of both modeling the dynamics as well as the mechanical design due to the short period of ground contact in which to actuate on the world. Previous work has demonstrated stable hopping on a moving-mass robot, wherein a single spring was utilized below the body of the robot. This paper finds that the addition of a spring in parallel to the actuator greatly improves the performance of moving mass hopping robots. This is demonstrated through the design of a novel one-dimensional hopping robot. For this robot, a rigorous trajectory optimization method is developed using hybrid systems models with experimentally tuned parameters. Simulation results are used to study the effects of a parallel spring on energetic efficiency, stability and hopping effort. We find that the double-spring model had 2.5x better energy efficiency than the single-spring model, and was able to hop using 40% less peak force from the actuator. Furthermore, the double-spring model produces stable hopping without the need for stabilizing controllers. These concepts are demonstrated experimentally on a novel hopping robot, wherein hop heights up to 40cm were achieved.

Parallel compliance design for increasing robustness and efficiency in legged locomotion - theoretical background and applications

“…Recent growing amount of research on parallel compliance in legged locomotion [11], [17], [18], [19], [16] shows the importance of this mechanical design feature. Compliance insertion in the robot hardware and actuator design mainly aims at reducing peak power, energy, or peak torque [13], [14].…”

“…Adding a parallel spring to the actuator not only reduces the control effort and increases energy efficiency, but also could improve stability [16]. Recently, a variety of modifications on PEA designs was presented such as LEAP [17], BIC-PEA [18] and SPEAR [19].…”

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“…The following are some of the advantages: Improved Performance: There are no human errors when a robot pharmacist fills and organizes vast quantities of drugs, unlike a human pharmacist. In addition to increasing operational efficiency, this frees up pharmacists' time to perform more value-added tasks 28 .…”

Hybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control Frequencies

“…Inspired by animal morphology and passive and active leg stiffness, legged robot designs often include mechanical springs ( Nasiri et al, 2016 ; Ambrose and Ames, 2020 ). Series elastic actuation (SEA) can simplify control, improve robustness and interaction safety, and protect actuators from overloads ( Raibert et al, 1984 ; Robinson et al, 1999 ; Pratt and Krupp, 2004 ; Hutter et al, 2011 ; Calanca et al, 2015 ; Hutter et al, 2016 ; AhmadSharbafi et al, 2020 ).…”

“…Series elastic actuation (SEA) can simplify control, improve robustness and interaction safety, and protect actuators from overloads ( Raibert et al, 1984 ; Robinson et al, 1999 ; Pratt and Krupp, 2004 ; Hutter et al, 2011 ; Calanca et al, 2015 ; Hutter et al, 2016 ; AhmadSharbafi et al, 2020 ). Designs with parallel mounted springs and actuators (parallel elastic actuation, PEA) can increase leg forces, improve locomotion energy efficiency, and reduce actuator loading ( Gunther et al, 2015 ; Niehues et al, 2015 ; Plooij et al, 2016 ; Yesilevskiy et al, 2016 ; Liu et al, 2018 ; Toxiri et al, 2018 ; Yesilevskiy et al, 2018 ; Roozing et al, 2019 ; Ambrose and Ames, 2020 ). Combined parallel and serial elastic designs have been proposed, leading to reduced peak torques and improved locomotion applicability ( Grimmer et al, 2012 ).…”